Currently, radiator fan modules are used to cool the engine in motor vehicles. A radiator fan module typically consists of a fan impeller, in which a motor to drive the fan impeller is arranged, and a frame which comprises mounting struts for fastening the fan impeller.
The fan impeller of a radiator fan module is generally designed to produce an air flow with which the heat generated by the engine of a motor vehicle is to be carried away. Radiator fan modules have what is known as a gap flow in addition to the main flow. The gap flow refers to the flow which forms between the fan impeller and the frame due to the pressure differential and which tends to swirl due to the rotation of the fan impeller. The swirling gap flow works against the main flow, leading to a negative impact on the flow behaviour of the radiator fan module. This defective flow sometimes leads to a very high level of undesirable noise being generated.